From Paris, where he had started out as assistant to Joseph Nicolas Delisle (1688–1768), Messier located Halley’s Comet on its 1758/9 return. He went on to discover some fifteen comets, plus six co-discoveries. During his searches he noted various objects (nebulae and star clusters) that could be mistaken for comets, starting with the Crab Nebula in 1758. His list of these objects became the Messier Catalogue.